The present invention relates to pumps, and more particularly, to reciprocating piston pumps used for pumping fluids which contain a high degree of suspended solids, and/or are at elevated temperatures and/or are corrosive.
When pumping certain fluids, for example heavy crude oils characterized by high contents of suspended solids, there is a problem with wear between the piston and cylinder of the pump. The wear results from the suspended particles in the pumped fluid which have a hardness which is greater than that of the metals used in the construction of various pump parts. These hard suspended particles find their way, for example, between the piston and cylinder wall of the pump and damage the piston and cylinder wall due to the hardness of the particles relative to the hardness of the metals used to construct the pump parts. The deterioration and wear of the pump parts is further increased when the pumped fluids are corrosive in nature and/or are at elevated temperatures. The wear on the piston and cylinder wall results in the passing of the pumped fluid between the piston and cylinder wall of the pump which results in a loss in volumentric efficiency of the pump.
In an attempt to overcome problems of wear associated with reciprocating piston pumps used for pumping fluids which contain a high degree of suspended solids, it has become commonplace in the prior art to provide removable metal liners for the pump cylinder which are readily inserted and replaced when worn. A typical arrangement of the type described above is disclosed in U.S. Pat. No. 1,528,097 to Cooper. In accordance with the '097 patent, a removable pump cylinder bushing made of a relatively low cost material is provided with a metal lining. The bushing is adapted to be readily replaced in the pump cylinder when the metal lining is worn. While the foregoing arrangement allows for a readily replaceable pump cylinder lining, it does not eliminate the wear problem on the cylinder nor on the operating piston. It is further known in the prior art to apply a wear-resistant alloy coating to bearing members in a piston pump as disclosed in U.S. Pat. No. 3,938,814 to Cromwell. Likewise, it has been proposed to spray a wearresistant layer of a ceramic material such as aluminum oxide on the running face of a sealing strip used on a vane in a rotary engine as disclosed in U.S. Pat. No. 4,016,635 to Leitermann et al. While the foregoing prior art patents teach the provision of applying wear-resistant coatings to working surfaces of pumps, the prior art fails to provide a mechanism for preventing wear in reciprocating piston pumps used for pumping fluids which contain a high degree of suspended solids while at the same time prohibiting the suspended solids from lodging between the piston and cylinder wall or, in the alternative, pulverize and destroy any solids which might lodge in that area.
Naturally, it is highly desirable to provide a reciprocating piston pump used for pumping fluids which contain a high degree of relatively hard suspended solids wherein the piston and cylinder wall of the pump are highly resistant to wear. The contacting surfaces of the piston and cylinder wall closely mate so as to prevent the suspended solids lodging between the piston or cylinder wall.
Accordingly, it is a principal object of the present invention to provide a reciprocating piston pump for pumping fluids containing a high degree of hard suspended particles which is highly resistant to wear.
It is a particular object of the present invention to provide a reciprocating piston pump wherein the metal piston is provided with an outer sleeve of a wear-resistant material which is slidingly received within a cylindrical sleeve of the same wear-resistant material mounted within the cylinder.
It is a further object of the present invention to provide a reciprocating piston pump wherein the contacting surface of the piston sleeve and cylindrical sleeve closely mate.
It is a still further object of the present invention to provide a reciprocating piston pump wherein the piston sleeve and cylindrical sleeve are made of a material characterized by a hardness of greater than nine on the Mho scale which is sufficient to pulverize any particles present in the pumped fluid.
It is still another further object of the present invention to provide a reciprocating piston pump wherein the piston sleeve and cylindrical sleeve are corrosion resistant.
Further objects and advantages will appear hereinbelow.